Polypropylene (PP) represents an important development direction for recyclable cable insulation materials. This paper investigates the synergistic improvement mechanism of the mechanical and electrical properties of PP. The effect of elastomers on the aggregation structure and carrier migration of the samples was investigated by analyzing the microstructure, crystallization, and mechanical and electrical properties of PP/elastomer composites. The results show that elastomers can reduce the tensile modulus of PP, while improving the tensile strength and elongation at break, thereby enhancing the mechanical properties of PP. The elastomer and the PP matrix have better compatibility and introduce amorphous regions, generating a large number of crystalline–amorphous interfaces, which introduce deep traps and reduce the mobility of carriers. Meanwhile, with an increase in elastomer content, the breakdown strength and volume resistivity both increase and then decrease. Among the samples tested, PP/PBE-2 has the best electrical properties and is the insulation material with the best mechanical and electrical properties. This study provides an important reference for the comprehensive performance regulation of PP insulation materials for high-voltage cables.

High-voltage (HV) cables may experience voltage polarity reversal during power adjustment, leading to the accumulation of space charges inside the insulation material and causing distortion of the internal electric field. To characterize the effect of grafting modification on the insulation properties of polypropylene (PP), various electrical properties were characterized. The results show that grafting modification can significantly improve the electrical properties of PP, with PPG-2 exhibiting the best electrical properties. Compared with PP, the breakdown strength of PPG-2 is increased by 39.27%, and the critical electric field is increased by 36.52%. Meanwhile, the charge accumulation inside the PPG-2 is extremely small after voltage polarity reversal. The mechanism of grafting modification to enhance the electrical properties of PP was explained by analyzing the trap characteristics of the samples. This indicates that grafting modification introduces a large number of deep traps within PP, suppressing the injection and migration of charge carriers. The presence of deep traps weakens the charge accumulation and electric field distortion at the interface. In this paper, the optimal monomer and content of grafted PP were determined, and the insulation properties of the cable under operating conditions were analyzed. The research results offer practical guidance for the development of high-performance grafted PP cable insulation materials and the reliability of cable operation.

The increasing demand for polymer dielectrics in different scenarios, such as electrical insulation cable, requires elevated electrical and mechanical properties. In order to understand the relationship between mechanical properties and the structure of grafted monomers in a grafted polypropylene (PP) system, a design framework based on the transfer-learning method has been proposed for designing grafted side chain structure in PP system. 22 samples of polypropylene-grafted polymer are synthesized. Through a well-trained multi-layer perceptron model for predicting glass transition temperature (Tg), mechanical properties of the grafted PP have been well predicted by the transfer-learning method. Meanwhile, the grafting group structures are divided into nine substructures. By assembling these substructures, the chemical space is established for prediction. Moreover, candidates with satisfied deep traps and flexible mechanical properties are screened out for reference. This work turns qualitative understanding into a quantitative analysis based on mathematical models and broadens the application of polymer materials design with a small dataset.